1. Field of the Invention
The present invention relates to the consolidation or solidification of mining deposits, e.g., coal fields, by injecting therein, and subsequently polymerizing, in situ, certain polymerizable polymer/monomer dispersions.
2. Description of the Prior Art
The complex art of consolidation or solidification of earth has long been replete with an abundance of literature reports in which the most diverse means have been proposed for resolving such problem. Nonetheless, insofar as the consolidation of mining beds, coal fields, ore and mineral deposits is concerned, and the difficult and complex problems with which the same is faced, the state of the art is conspicuously devoid of more than but a few meaningful solutions. In fact, in addition to the inherent difficulties in any ground consolidation process, which arise from the nature of the land, from its cohesiveness, looseness and/or compactness, and from the nature and state of any fissures or "seams" permeating same, such mining sites are also subject to the effects of the pressure in the ground, which effects are caused by working, and especially by the dynamics involved in the progression of the stopes. Furthermore, since any injection of a consolidating material, for example, is carried out, by definition, near a face surface, it is not possible to use injection pressures which are relatively high, because such pressures likely would cause rupturing of the earth body instead of consolidating same. And in addition to these problems which are mechanical in nature, there too are safety problems, and it is a truism that the use of flammable materials and/or materials which are capable of evolving toxic substances is definitely not recommended in mining excavations. Further along these lines, the technique proposed in French Patent Application No. 2,279,891, namely, the use of resins of polyurethane type, is not entirely satisfactory. According to this patent (page 2, lines 29 to 32), such products, once polymerized, exhibit great flexibility, and display high values for modulus of elasticity and flexural strength, and they also develop a significant binding or adhesive force between the coal and the surrounding rock, stone or ground. Contrariwise, it too is known, on the one hand, that polyurethanes are flammable materials and that their combustion releases carbon monoxide and hydrocyanic acid; while on the other hand, when carrying out a consolidation by injection under pressure, the recommended pressure, according to the patent (page 11, line 18), is quite high (60 bars).